1. Field of the Invention
The present invention relates to an apparatus for winding a roving applied to each draft part of a roving frame, and more particularly, to an apparatus for winding a roving applied to each draft part of a roving frame of a bobbin lead winding system.
2. Description of the Related Arts
In the conventional roving frame, a roving delivered from each draft part is wound on a bobbin which is rotating at a predetermined higher speed than the rotational speed of a flyer, while providing twists on the roving. In this winding system, if the delivered length of the roving from the draft part per a unit of time does not match the winding length of the roving per the identical unit of time, in accordance with an increase of the diameter of a roving package formed on the bobbin, it is impossible to carry out a normal winding, and thus the winding tension of the roving is varied and breakages of the roving occur during the winding operation.
To solve the above problem, a cone drum type speed regulating device utilizing a pair of cone drums is commonly applied to a conventional roving frame. In this speed regulating device, the pair of cone drums comprises a driving cone drum and a driven cone drum, and the driven cone drum is driven by the driving cone drum through an endless belt which can be shifted along the axial direction of the cone drums. The shapes of these cone drums are designed to obtain the required regulation of the rotational speed of the bobbin relative to the constant rotational speed of the flyer, in accordance with an increase of the diameter of the package of each roving bobbin.
As mentioned above, in the cone drum type speed regulating device, the shape of the cone drums is designed so as to satisfy the predetermined spinning condition regarding the speed relationship between two cone drums, but the shape of the cone drums can be modified if a particular spinning condition is required. If a particular spinning condition is required, the displacement of the belt shifter is adjusted by a supplemental cam mechanism. Japanese Examined Utility Model Publication Showa 52 (1977)--13376, and Japanese Examined Patent Publication Showa 52 (1977)--48652 disclose the device mentioned above, but such a modified device has the disadvantages of a complicated operation when adjusting the device, the need for a relatively large space for the installation thereof, and a labor-consuming maintenance operation. Moreover, a complicated additional mechanism is needed to return the belt to a position for starting the winding operation.
To solve the above-mentioned problems, Japanese Unexamined Patent Publication Showa 63 (1988)--264923 provides a system utilizating a variable speed motor to drive bobbin wheels, i.e., a bobbin shaft, independently from the draft parts, wherein the driving speed of the bobbin shaft is controlled based upon a predetermined spinning condition. Namely, in this system, the variable speed motor is driven under variable conditions by means of an inverter, with suitable driving speeds of the bobbin shaft for forming particular portions of the roving bobbin being computed by a computer, based upon the delivery speed of a common bottom front roller of the draft parts and predetermined spinning conditions input to the computer. The speed of the variable speed motor is controlled in accordance with signals indicating changes in the direction of displacement of the bobbin rail. In this system, the above-mentioned cone drum speed regulating device can be omitted, thus removing the problems mentioned above. Nevertheless, since the rotation of the bobbin shaft is controlled in terms of the driving speed thereof, it is necessary to utilize a device to detect the delivery speed of the bottom front roller, and if the above-mentioned detector is an analog type unit, it is impossible to precisely control the driving speed of the bobbin shaft because the function of the detector is easily affected by changes of temperature, and if the above-mentioned speed detector is a digital type, it is impossible to precisely control the rotational speed of the bobbin shaft. Namely, if a digital type speed detector is utilized to detect the rotational speed of the bottom front roller, since the rotational speed of the bottom front roller is represented by the number of rotations of the bottom front roller per a unit of time, it is necessary to compute the rotational speed of the bottom front roller by a computer, and therefore, the above-mentioned computation must be carried out at each elapse of the above-mentioned unit of time, and thus the computed data can be obtained only at each elapse of the above-mentioned unit of time. In the above-mentioned case, the rotational speed, which is represented by analog data, of the variable speed motor is controlled by an inverter, and this control system is also affected by the temperature of a zone surrounding the control system. Further, if a commercially available inverter is utilized, the range of the control capacity of such an inverter is limited, and therefore, if it is necessary to control the variable speed motor within a range below the lower limit of the allowed frequency, the rotational speed of the variable speed motor cannot be maintained below the above-mentioned lower limit of the frequency. Accordingly, the response at the time of switching the roving frame and at the time of stopping the roving frame is not good.